/* composite an array of images with PDF operators
 *
 * 25/9/17
 * 	- from bandjoin.c
 * 30/11/17
 * 	- add composite2 class, to make a nice CLI interface
 * 30/1/18
 * 	- remove number of images limit
 * 	- allow one mode ... reused for all joins
 * 11/8/18 [medakk]
 * 	- x/y params let you position images
 * 27/11/18
 * 	- don't stop on first non-transparent image [felixbuenemann, GDmac]
 * 6/12/18
 *	- do our own subimage positioning
 * 8/5/19
 * 	- revise in/out/dest-in/dest-out to make smoother alpha
 */

/*

	This file is part of VIPS.

	VIPS is free software; you can redistribute it and/or modify
	it under the terms of the GNU Lesser General Public License as published by
	the Free Software Foundation; either version 2 of the License, or
	(at your option) any later version.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU Lesser General Public License for more details.

	You should have received a copy of the GNU Lesser General Public License
	along with this program; if not, write to the Free Software
	Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
	02110-1301  USA

 */

/*

	These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk

 */

/*
#define VIPS_DEBUG
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif /*HAVE_CONFIG_H*/
#include <glib/gi18n-lib.h>

#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>

#if defined(HAVE__ALIGNED_MALLOC) || defined(HAVE_MEMALIGN)
#include <malloc.h>
#endif

#include <vips/vips.h>
#include <vips/internal.h>
#include <vips/debug.h>

#include "pconversion.h"

/* Maximum number of image bands.
 */
#define MAX_BANDS (64)

/* Uncomment to disable the vector path ... handy for debugging.
#undef HAVE_VECTOR_ARITH
 */

/* We have a vector path with gcc's vector attr.
 */
#ifdef HAVE_VECTOR_ARITH
/* A vector of four floats.
 */
typedef float v4f __attribute__((vector_size(4 * sizeof(float)), aligned(16)));
#endif /*HAVE_VECTOR_ARITH*/

typedef struct _VipsCompositeBase {
	VipsConversion parent_instance;

	/* The input images.
	 */
	VipsArrayImage *in;

	/* For N input images, 1 blend mode or N - 1 blend modes.
	 */
	VipsArrayInt *mode;

	/* Compositing space. This defaults to RGB, or B_W if we only have
	 * G and GA inputs.
	 */
	VipsInterpretation compositing_space;

	/* Set if the input images have already been premultiplied.
	 */
	gboolean premultiplied;

	/* The x and y positions for each image in the stack. There are n - 1
	 * of these, since image 0 is always positioned at (0, 0). Set by
	 * subclasses. Can be NULL.
	 */
	int *x_offset;
	int *y_offset;

	/* A rect for the position of each input image. For each output region,
	 * we composite the set of input images which intersect that area.
	 */
	VipsRect *subimages;

	/* The number of non-alpha bands we are blending.
	 */
	int bands;

	/* The maximum value for each band, set from the image interpretation.
	 * This is used to scale each band to 0 - 1.
	 */
	double max_band[MAX_BANDS + 1];

	/* TRUE if all our modes are skippable, ie. we can avoid compositing
	 * the whole stack for every pixel request.
	 */
	gboolean skippable;

} VipsCompositeBase;

typedef VipsConversionClass VipsCompositeBaseClass;

/* We need C linkage for this.
 */
extern "C" {
G_DEFINE_ABSTRACT_TYPE(VipsCompositeBase, vips_composite_base,
	VIPS_TYPE_CONVERSION);
}

static void
vips_composite_base_dispose(GObject *gobject)
{
	VipsCompositeBase *composite = (VipsCompositeBase *) gobject;

	if (composite->in) {
		vips_area_unref((VipsArea *) composite->in);
		composite->in = nullptr;
	}
	if (composite->mode) {
		vips_area_unref((VipsArea *) composite->mode);
		composite->mode = nullptr;
	}
	VIPS_FREE(composite->subimages);

	G_OBJECT_CLASS(vips_composite_base_parent_class)->dispose(gobject);
}

/* Our sequence value.
 */
typedef struct {
#ifdef HAVE_VECTOR_ARITH
	/* max_band as a vector, for the RGBA case. This must be
	 * defined first to ensure that the member is aligned
	 * on a 16-byte boundary.
	 */
	v4f max_band_vec;
#endif /*HAVE_VECTOR_ARITH*/

	VipsCompositeBase *composite;

	/* Full set of input regions, each made on the corresponding input
	 * image.
	 */
	VipsRegion **input_regions;

	/* We then vips_region_prepare_to() to one of this set of regions,
	 * each defined on the base image.
	 */
	VipsRegion **composite_regions;

	/* Number of input regions which intersect this request rect.
	 */
	int n;

	/* For each of @n above (inputs which intersect this request), the
	 * index of the input image we need. We can use this index to get the
	 * position, input region and composite region.
	 */
	int *enabled;

	/* For each enabled image, an input pointer.
	 */
	VipsPel **p;

} VipsCompositeSequence;

#ifdef HAVE_VECTOR_ARITH
/* Allocate aligned memory. The return value can be released
 * by calling the vips_free_aligned() function, for example:
 * VIPS_FREEF(vips_free_aligned, ptr);
 */
static inline void *
vips_alloc_aligned(size_t sz, size_t align)
{
	g_assert(!(align & (align - 1)));

#ifdef HAVE__ALIGNED_MALLOC
	return _aligned_malloc(sz, align);
#elif defined(HAVE_POSIX_MEMALIGN)
	void *ptr;
	if (posix_memalign(&ptr, align, sz))
		return nullptr;
	return ptr;
#elif defined(HAVE_MEMALIGN)
	return memalign(align, sz);
#else
#error Missing aligned alloc implementation
#endif
}

static inline void
vips_free_aligned(void *ptr)
{
#ifdef HAVE__ALIGNED_MALLOC
	_aligned_free(ptr);
#else /*defined(HAVE_POSIX_MEMALIGN) || defined(HAVE_MEMALIGN)*/
	free(ptr);
#endif
}
#endif /*HAVE_VECTOR_ARITH*/

static int
vips_composite_stop(void *vseq, void *a, void *b)
{
	VipsCompositeSequence *seq = (VipsCompositeSequence *) vseq;

	if (seq->input_regions) {
		for (int i = 0; seq->input_regions[i]; i++)
			VIPS_UNREF(seq->input_regions[i]);
		VIPS_FREE(seq->input_regions);
	}

	if (seq->composite_regions) {
		for (int i = 0; seq->composite_regions[i]; i++)
			VIPS_UNREF(seq->composite_regions[i]);
		VIPS_FREE(seq->composite_regions);
	}

	VIPS_FREE(seq->enabled);
	VIPS_FREE(seq->p);

#ifdef HAVE_VECTOR_ARITH
	VIPS_FREEF(vips_free_aligned, seq);
#else  /*!defined(HAVE_VECTOR_ARITH)*/
	VIPS_FREE(seq);
#endif /*HAVE_VECTOR_ARITH*/

	return 0;
}

static void *
vips_composite_start(VipsImage *out, void *a, void *b)
{
	VipsImage **in = (VipsImage **) a;
	VipsCompositeBase *composite = (VipsCompositeBase *) b;

	VipsCompositeSequence *seq;
	int i, n;

#ifdef HAVE_VECTOR_ARITH
	/* Ensure that the memory is aligned on a 16-byte boundary.
	 */
	if (!(seq = ((VipsCompositeSequence *) vips_alloc_aligned(
			  sizeof(VipsCompositeSequence), 16))))
#else  /*!defined(HAVE_VECTOR_ARITH)*/
	if (!(seq = VIPS_NEW(NULL, VipsCompositeSequence)))
#endif /*HAVE_VECTOR_ARITH*/
		return nullptr;

	seq->composite = composite;
	seq->input_regions = nullptr;
	seq->enabled = nullptr;
	seq->p = nullptr;

	/* How many images?
	 */
	for (n = 0; in[n]; n++)
		;

	/* Allocate space for region array.
	 */
	if (!(seq->input_regions = VIPS_ARRAY(NULL, n + 1, VipsRegion *))) {
		vips_composite_stop(seq, nullptr, nullptr);
		return nullptr;
	}
	for (i = 0; i < n + 1; i++)
		seq->input_regions[i] = nullptr;

	if (!(seq->composite_regions =
				VIPS_ARRAY(NULL, n + 1, VipsRegion *))) {
		vips_composite_stop(seq, nullptr, nullptr);
		return nullptr;
	}
	for (i = 0; i < n + 1; i++)
		seq->composite_regions[i] = nullptr;

	seq->enabled = VIPS_ARRAY(NULL, n, int);
	seq->p = VIPS_ARRAY(NULL, n, VipsPel *);
	if (!seq->enabled ||
		!seq->p) {
		vips_composite_stop(seq, nullptr, nullptr);
		return nullptr;
	}

	/* Create a set of regions.
	 */
	for (i = 0; i < n; i++) {
		seq->input_regions[i] = vips_region_new(in[i]);
		seq->composite_regions[i] = vips_region_new(in[0]);

		if (!seq->input_regions[i] ||
			!seq->composite_regions[i]) {
			vips_composite_stop(seq, nullptr, nullptr);
			return nullptr;
		}
	}

#ifdef HAVE_VECTOR_ARITH
	/* We need a float version for the vector path.
	 */
	if (composite->bands == 3)
		seq->max_band_vec = (v4f){
			(float) composite->max_band[0],
			(float) composite->max_band[1],
			(float) composite->max_band[2],
			(float) composite->max_band[3]
		};
#endif

	return seq;
}

/* For each of the supported interpretations, the maximum value of each band.
 */
static int
vips_composite_base_max_band(VipsCompositeBase *composite, double *max_band)
{
	double max_alpha;
	int b;

	max_alpha = vips_interpretation_max_alpha(composite->compositing_space);

	for (b = 0; b <= composite->bands; b++)
		max_band[b] = max_alpha;

	switch (composite->compositing_space) {
	case VIPS_INTERPRETATION_XYZ:
		max_band[0] = VIPS_D65_X0;
		max_band[1] = VIPS_D65_Y0;
		max_band[2] = VIPS_D65_Z0;
		break;

	case VIPS_INTERPRETATION_LAB:
		max_band[0] = 100;
		max_band[1] = 128;
		max_band[2] = 128;
		break;

	case VIPS_INTERPRETATION_LCH:
		max_band[0] = 100;
		max_band[1] = 128;
		max_band[2] = 360;
		break;

	case VIPS_INTERPRETATION_CMC:
		max_band[0] = 100;
		max_band[1] = 128;
		max_band[2] = 360;
		break;

	case VIPS_INTERPRETATION_scRGB:
		max_band[0] = 1;
		max_band[1] = 1;
		max_band[2] = 1;
		break;

	case VIPS_INTERPRETATION_sRGB:
		max_band[0] = 255;
		max_band[1] = 255;
		max_band[2] = 255;
		break;

	case VIPS_INTERPRETATION_HSV:
		max_band[0] = 255;
		max_band[1] = 255;
		max_band[2] = 255;
		break;

	case VIPS_INTERPRETATION_CMYK:
		max_band[0] = 255;
		max_band[1] = 255;
		max_band[2] = 255;
		max_band[3] = 255;
		break;

	case VIPS_INTERPRETATION_RGB16:
		max_band[0] = 65535;
		max_band[1] = 65535;
		max_band[2] = 65535;
		break;

	case VIPS_INTERPRETATION_GREY16:
		max_band[0] = 65535;
		break;

	case VIPS_INTERPRETATION_YXY:
		max_band[0] = 100;
		max_band[1] = 1;
		max_band[2] = 1;
		break;

	case VIPS_INTERPRETATION_B_W:
		max_band[0] = 255;
		break;

	default:
		return -1;
	}

	return 0;
}

/* Find the subset of our input images which intersect this region. If we are
 * not in skippable mode, we must enable all layers.
 */
static void
vips_composite_base_select(VipsCompositeSequence *seq, VipsRect *r)
{
	VipsCompositeBase *composite = seq->composite;
	int n = composite->in->area.n;

	seq->n = 0;
	for (int i = 0; i < n; i++)
		if (!composite->skippable ||
			vips_rect_overlapsrect(r,
				&composite->subimages[i])) {
			seq->enabled[seq->n] = i;
			seq->n += 1;
		}
}

/* Cairo naming conventions:
 *
 * aR	alpha of result
 * aA	alpha of source A	(the new pixel)
 * aB	alpha of source B	(the thing we accumulate)
 * xR	colour band of result
 * xA	colour band of source A
 * xB	colour band of source B
 */

/* A is the new pixel coming in, of any non-complex type T.
 *
 * We must scale incoming pixels to 0 - 1 by dividing by the scale[] vector.
 *
 * If premultipled is not set, we premultiply incoming pixels before blending.
 *
 * B is the double pixel we are accumulating.
 */
template <typename T>
static void
vips_composite_base_blend(VipsCompositeBase *composite,
	VipsBlendMode mode, double *restrict B, T *restrict p)
{
	const int bands = composite->bands;

	double A[MAX_BANDS + 1];
	double aA;
	double aB;
	double aR;
	double t1;
	double t2;
	double t3;
	double f[MAX_BANDS + 1];

	/* Load and scale the pixel to 0 - 1.
	 */
	for (int b = 0; b <= bands; b++)
		A[b] = p[b] / composite->max_band[b];
	/* Not necessary, but it stops a compiler warning.
	 */
	for (int b = bands + 1; b < MAX_BANDS + 1; b++)
		A[b] = 0.0;

	aA = A[bands];
	aB = B[bands];

	/* We may need to premultiply A.
	 */
	if (!composite->premultiplied)
		for (int b = 0; b < bands; b++)
			A[b] *= aA;

	switch (mode) {
	case VIPS_BLEND_MODE_CLEAR:
		aR = 0;
		for (int b = 0; b < bands; b++)
			B[b] = 0;
		break;

	case VIPS_BLEND_MODE_SOURCE:
		aR = aA;
		for (int b = 0; b < bands; b++)
			B[b] = A[b];
		break;

	case VIPS_BLEND_MODE_OVER:
		aR = aA + aB * (1 - aA);
		t1 = 1 - aA;
		for (int b = 0; b < bands; b++)
			B[b] = A[b] + t1 * B[b];
		break;

	case VIPS_BLEND_MODE_IN:
		aR = aA * aB;
		// if aA == 0, then aR == 0 and so B will already be 0
		if (aA != 0)
			for (int b = 0; b < bands; b++)
				B[b] = A[b] * aR / aA;
		break;

	case VIPS_BLEND_MODE_OUT:
		aR = aA * (1 - aB);
		// if aA == 0, then aR == 0 and so B will already be 0
		if (aA != 0)
			for (int b = 0; b < bands; b++)
				B[b] = A[b] * aR / aA;
		break;

	case VIPS_BLEND_MODE_ATOP:
		aR = aB;
		t1 = 1 - aA;
		for (int b = 0; b < bands; b++)
			B[b] = A[b] + t1 * B[b];
		break;

	case VIPS_BLEND_MODE_DEST:
		aR = aB;
		// B = B
		break;

	case VIPS_BLEND_MODE_DEST_OVER:
		aR = aB + aA * (1 - aB);
		t1 = 1 - aB;
		for (int b = 0; b < bands; b++)
			B[b] = B[b] + t1 * A[b];
		break;

	case VIPS_BLEND_MODE_DEST_IN:
		aR = aA * aB;
		// B = B
		if (aB != 0)
			for (int b = 0; b < bands; b++)
				B[b] *= aR / aB;
		break;

	case VIPS_BLEND_MODE_DEST_OUT:
		aR = (1 - aA) * aB;
		// B = B
		// if aB is 0, then B is already 0
		if (aB != 0)
			for (int b = 0; b < bands; b++)
				B[b] *= aR / aB;
		break;

	case VIPS_BLEND_MODE_DEST_ATOP:
		aR = aA;
		t1 = 1 - aB;
		for (int b = 0; b < bands; b++)
			B[b] = t1 * A[b] + B[b];
		break;

	case VIPS_BLEND_MODE_XOR:
		aR = aA + aB - 2 * aA * aB;
		t1 = 1 - aB;
		t2 = 1 - aA;
		for (int b = 0; b < bands; b++)
			B[b] = t1 * A[b] + t2 * B[b];
		break;

	case VIPS_BLEND_MODE_ADD:
		aR = VIPS_MIN(1, aA + aB);
		for (int b = 0; b < bands; b++)
			B[b] = A[b] + B[b];
		break;

	case VIPS_BLEND_MODE_SATURATE:
		aR = VIPS_MIN(1, aA + aB);
		t1 = VIPS_MIN(aA, 1 - aB);
		for (int b = 0; b < bands; b++)
			B[b] = t1 * A[b] + B[b];
		break;

	default:
		/* The PDF modes are a bit different.
		 */
		aR = aA + aB * (1 - aA);

		switch (mode) {
		case VIPS_BLEND_MODE_MULTIPLY:
			for (int b = 0; b < bands; b++)
				f[b] = A[b] * B[b];
			break;

		case VIPS_BLEND_MODE_SCREEN:
			for (int b = 0; b < bands; b++)
				f[b] = A[b] + B[b] - A[b] * B[b];
			break;

		case VIPS_BLEND_MODE_OVERLAY:
			for (int b = 0; b < bands; b++)
				if (B[b] <= 0.5)
					f[b] = 2 * A[b] * B[b];
				else
					f[b] = 1 - 2 * (1 - A[b]) * (1 - B[b]);
			break;

		case VIPS_BLEND_MODE_DARKEN:
			for (int b = 0; b < bands; b++)
				f[b] = VIPS_MIN(A[b], B[b]);
			break;

		case VIPS_BLEND_MODE_LIGHTEN:
			for (int b = 0; b < bands; b++)
				f[b] = VIPS_MAX(A[b], B[b]);
			break;

		case VIPS_BLEND_MODE_COLOUR_DODGE:
			for (int b = 0; b < bands; b++)
				if (A[b] < 1)
					f[b] = VIPS_MIN(1, B[b] / (1 - A[b]));
				else
					f[b] = 1;
			break;

		case VIPS_BLEND_MODE_COLOUR_BURN:
			for (int b = 0; b < bands; b++)
				if (A[b] > 0)
					f[b] = 1 - VIPS_MIN(1, (1 - B[b]) / A[b]);
				else
					f[b] = 0;
			break;

		case VIPS_BLEND_MODE_HARD_LIGHT:
			for (int b = 0; b < bands; b++)
				if (A[b] <= 0.5)
					f[b] = 2 * A[b] * B[b];
				else
					f[b] = 1 - 2 * (1 - A[b]) * (1 - B[b]);
			break;

		case VIPS_BLEND_MODE_SOFT_LIGHT:
			for (int b = 0; b < bands; b++) {
				double g;

				if (B[b] <= 0.25)
					g = ((16 * B[b] - 12) * B[b] + 4) * B[b];
				else
					g = sqrt(B[b]);

				if (A[b] <= 0.5)
					f[b] = B[b] - (1 - 2 * A[b]) * B[b] * (1 - B[b]);
				else
					f[b] = B[b] + (2 * A[b] - 1) * (g - B[b]);
			}
			break;

		case VIPS_BLEND_MODE_DIFFERENCE:
			for (int b = 0; b < bands; b++)
				f[b] = fabs(B[b] - A[b]);
			break;

		case VIPS_BLEND_MODE_EXCLUSION:
			for (int b = 0; b < bands; b++)
				f[b] = A[b] + B[b] - 2 * A[b] * B[b];
			break;

		default:
			g_assert_not_reached();
			for (int b = 0; b < bands; b++)
				B[b] = 0;
		}

		t1 = 1 - aB;
		t2 = 1 - aA;
		t3 = aA * aB;
		for (int b = 0; b < bands; b++)
			B[b] = t1 * A[b] + t2 * B[b] + t3 * f[b];
		break;
	}

	B[bands] = aR;
}

/* We have a vector path with gcc's vector attr.
 */
#ifdef HAVE_VECTOR_ARITH
/* Special path for RGBA with non-double output. This is overwhelmingly the
 * most common case, and vectorises easily.
 *
 * B is the float pixel we are accumulating, A is the new pixel coming
 * in from memory.
 */
template <typename T>
static void
vips_composite_base_blend3(VipsCompositeSequence *seq,
	VipsBlendMode mode, v4f &B, T *restrict p)
{
	VipsCompositeBase *composite = seq->composite;

	v4f A;
	float aA;
	float aB;
	float aR;
	float t1;
	float t2;
	float t3;
	v4f f;
	v4f g;

	/* Load and scale the pixel to 0 - 1.
	 */
	A[0] = p[0];
	A[1] = p[1];
	A[2] = p[2];
	A[3] = p[3];

	A /= seq->max_band_vec;

	aA = A[3];
	aB = B[3];

	/* We may need to premultiply A.
	 */
	if (!composite->premultiplied)
		A *= aA;

	/* See https://www.cairographics.org/operators for a nice summary of
	 * the operators and their meaning.
	 *
	 * Some operators need the unpremultiplied values (eg. dest-in), so
	 * we have to do an extra unpremultiply/premultiply.
	 */

	switch (mode) {
	case VIPS_BLEND_MODE_CLEAR:
		aR = 0;
		B[0] = 0;
		B[1] = 0;
		B[2] = 0;
		break;

	case VIPS_BLEND_MODE_SOURCE:
		aR = aA;
		B = A;
		break;

	case VIPS_BLEND_MODE_OVER:
		aR = aA + aB * (1 - aA);
		t1 = 1 - aA;
		B = A + t1 * B;
		break;

	case VIPS_BLEND_MODE_IN:
		aR = aA * aB;
		// if aA == 0, then aR == 0 and so B will already be 0
		if (aA != 0)
			B = A * aR / aA;
		break;

	case VIPS_BLEND_MODE_OUT:
		aR = aA * (1 - aB);
		// if aA == 0, then aR == 0 and so B will already be 0
		if (aA != 0)
			B = A * aR / aA;
		break;

	case VIPS_BLEND_MODE_ATOP:
		aR = aB;
		t1 = 1 - aA;
		B = A + t1 * B;
		break;

	case VIPS_BLEND_MODE_DEST:
		aR = aB;
		// B = B
		break;

	case VIPS_BLEND_MODE_DEST_OVER:
		aR = aB + aA * (1 - aB);
		t1 = 1 - aB;
		B = B + t1 * A;
		break;

	case VIPS_BLEND_MODE_DEST_IN:
		aR = aA * aB;
		// if aB is 0, then B is already 0
		if (aB != 0)
			B *= aR / aB;
		break;

	case VIPS_BLEND_MODE_DEST_OUT:
		aR = (1 - aA) * aB;
		// B = B
		// if aB is 0, then B is already 0
		if (aB != 0)
			B *= aR / aB;
		break;

	case VIPS_BLEND_MODE_DEST_ATOP:
		aR = aA;
		t1 = 1 - aB;
		B = t1 * A + B;
		break;

	case VIPS_BLEND_MODE_XOR:
		aR = aA + aB - 2 * aA * aB;
		t1 = 1 - aB;
		t2 = 1 - aA;
		B = t1 * A + t2 * B;
		break;

	case VIPS_BLEND_MODE_ADD:
		aR = VIPS_MIN(1, aA + aB);
		B = A + B;
		break;

	case VIPS_BLEND_MODE_SATURATE:
		aR = VIPS_MIN(1, aA + aB);
		t1 = VIPS_MIN(aA, 1 - aB);
		B = t1 * A + B;
		break;

	default:
		/* The PDF modes are a bit different.
		 */
		aR = aA + aB * (1 - aA);

		switch (mode) {
		case VIPS_BLEND_MODE_MULTIPLY:
			f = A * B;
			break;

		case VIPS_BLEND_MODE_SCREEN:
			f = A + B - A * B;
			break;

		case VIPS_BLEND_MODE_OVERLAY:
			f = B <= 0.5f
				? 2 * A * B
				: 1 - 2 * (1 - A) * (1 - B);
			break;

		case VIPS_BLEND_MODE_DARKEN:
			f = VIPS_MIN(A, B);
			break;

		case VIPS_BLEND_MODE_LIGHTEN:
			f = VIPS_MAX(A, B);
			break;

		case VIPS_BLEND_MODE_COLOUR_DODGE:
			f = A < 1
				? VIPS_MIN(1, B / (1 - A))
				: 1;
			break;

		case VIPS_BLEND_MODE_COLOUR_BURN:
			f = A > 0
				? 1 - VIPS_MIN(1, (1 - B) / A)
				: 0;
			break;

		case VIPS_BLEND_MODE_HARD_LIGHT:
			f = A <= 0.5f
				? 2 * A * B
				: 1 - 2 * (1 - A) * (1 - B);
			break;

		case VIPS_BLEND_MODE_SOFT_LIGHT:
			/* You can't sqrt a vector, so we must loop.
			 */
			for (int b = 0; b < 3; b++) {
				float g;

				if (B[b] <= 0.25)
					g = ((16 * B[b] - 12) * B[b] + 4) * B[b];
				else
					g = sqrt(B[b]);

				if (A[b] <= 0.5)
					f[b] = B[b] - (1 - 2 * A[b]) * B[b] * (1 - B[b]);
				else
					f[b] = B[b] + (2 * A[b] - 1) * (g - B[b]);
			}
			break;

		case VIPS_BLEND_MODE_DIFFERENCE:
			g = B - A;
			f = g > 0 ? g : -1 * g;
			break;

		case VIPS_BLEND_MODE_EXCLUSION:
			f = A + B - 2 * A * B;
			break;

		default:
			g_assert_not_reached();

			/* Stop compiler warnings.
			 */
			for (int b = 0; b < 3; b++)
				B[b] = 0;
			f = A;
		}

		t1 = 1 - aB;
		t2 = 1 - aA;
		t3 = aA * aB;
		B = t1 * A + t2 * B + t3 * f;
		break;
	}

	B[3] = aR;
}
#endif /*HAVE_VECTOR_ARITH*/

/* min_T and max_T are the numeric range for this type. 0, 0 means no limit,
 * for example float.
 */
template <typename T, gint64 min_T, gint64 max_T>
static void
vips_combine_pixels(VipsCompositeSequence *seq, VipsPel *q)
{
	VipsCompositeBase *composite = seq->composite;
	VipsBlendMode *mode = (VipsBlendMode *) composite->mode->area.data;
	int n_mode = composite->mode->area.n;
	int n = seq->n;
	int bands = composite->bands;
	T *restrict tq = (T *restrict) q;
	T **restrict tp = (T * *restrict) seq->p;

	double B[MAX_BANDS + 1] = { 0.0 };
	double aB;

	/* Load and scale the base pixel to 0 - 1.
	 */
	for (int b = 0; b <= bands; b++)
		B[b] = tp[0][b] / composite->max_band[b];

	aB = B[bands];
	if (!composite->premultiplied)
		for (int b = 0; b < bands; b++)
			B[b] *= aB;

	for (int i = 1; i < n; i++) {
		int j = seq->enabled[i];
		VipsBlendMode m = n_mode == 1 ? mode[0] : mode[j - 1];

		vips_composite_base_blend<T>(composite, m, B, tp[i]);
	}

	/* Unpremultiply, if necessary.
	 */
	if (!composite->premultiplied) {
		double aR = B[bands];

		if (aR == 0)
			for (int b = 0; b < bands; b++)
				B[b] = 0;
		else
			for (int b = 0; b < bands; b++)
				B[b] = B[b] / aR;
	}

	/* Write back as a full range pixel, clipping to range.
	 */
	for (int b = 0; b <= bands; b++) {
		double v;

		v = B[b] * composite->max_band[b];
		if (min_T != 0 ||
			max_T != 0) {
			v = VIPS_CLIP(min_T, v, max_T);
		}

		tq[b] = v;
	}
}

#ifdef HAVE_VECTOR_ARITH
/* Three band (four with alpha) vector case. Non-double output. min_T and
 * max_T are the numeric range for this type. 0, 0 means no limit,
 * for example float.
 */
template <typename T, gint64 min_T, gint64 max_T>
static void
vips_combine_pixels3(VipsCompositeSequence *seq, VipsPel *q)
{
	VipsCompositeBase *composite = seq->composite;
	VipsBlendMode *mode = (VipsBlendMode *) composite->mode->area.data;
	int n_mode = composite->mode->area.n;
	int n = seq->n;
	T *restrict tq = (T *restrict) q;
	T **restrict tp = (T * *restrict) seq->p;

	v4f B;
	float aB;

	B[0] = tp[0][0];
	B[1] = tp[0][1];
	B[2] = tp[0][2];
	B[3] = tp[0][3];

	/* Scale the base pixel to 0 - 1.
	 */
	B /= seq->max_band_vec;
	aB = B[3];

	if (!composite->premultiplied) {
		B *= aB;
		B[3] = aB;
	}

	for (int i = 1; i < n; i++) {
		int j = seq->enabled[i];
		VipsBlendMode m = n_mode == 1 ? mode[0] : mode[j - 1];

		vips_composite_base_blend3<T>(seq, m, B, tp[i]);
	}

	/* Unpremultiply, if necessary.
	 */
	if (!composite->premultiplied) {
		float aR = B[3];

		if (aR == 0)
			for (int b = 0; b < 3; b++)
				B[b] = 0;
		else {
			B /= aR;
			B[3] = aR;
		}
	}

	/* Write back as a full range pixel, clipping to range.
	 */
	B *= seq->max_band_vec;
	if (min_T != 0 ||
		max_T != 0) {
		float low = min_T;
		float high = max_T;

		B = VIPS_CLIP(low, B, high);
	}

	tq[0] = B[0];
	tq[1] = B[1];
	tq[2] = B[2];
	tq[3] = B[3];
}
#endif /*HAVE_VECTOR_ARITH*/

static int
vips_composite_base_gen(VipsRegion *output_region,
	void *vseq, void *a, void *b, gboolean *stop)
{
	VipsCompositeSequence *seq = (VipsCompositeSequence *) vseq;
	VipsCompositeBase *composite = (VipsCompositeBase *) b;
	VipsRect *r = &output_region->valid;
	int ps = VIPS_IMAGE_SIZEOF_PEL(output_region->im);

	VIPS_DEBUG_MSG("vips_composite_base_gen: at %d x %d, size %d x %d\n",
		r->left, r->top, r->width, r->height);

	/* Find the subset of our input images which intersect this region.
	 */
	vips_composite_base_select(seq, r);

	VIPS_DEBUG_MSG("  selected %d images\n", seq->n);

	/* Is there just one? We can prepare directly to output and return.
	 */
	if (seq->n == 1) {
		/* This can only be the background image, since it's the only
		 * image which exactly fills the whole output.
		 */
		g_assert(seq->enabled[0] == 0);

		if (vips_region_prepare(seq->input_regions[0], r))
			return -1;
		if (vips_region_region(output_region, seq->input_regions[0],
				r, r->left, r->top))
			return -1;

		return 0;
	}

	/* Prepare the appropriate parts into our set of composite
	 * regions.
	 */
	for (int i = 0; i < seq->n; i++) {
		int j = seq->enabled[i];

		VipsRect hit;
		VipsRect request;

		/* Set the composite region up to be a bit of memory at the
		 * right position.
		 */
		if (vips_region_buffer(seq->composite_regions[j], r))
			return -1;

		/* Clip against this subimage position and size.
		 */
		hit = *r;
		vips_rect_intersectrect(&hit, &composite->subimages[j], &hit);

		/* Translate request to subimage coordinates.
		 */
		request = hit;
		request.left -= composite->subimages[j].left;
		request.top -= composite->subimages[j].top;

		/* If the request is smaller than the target region, there
		 * will be some gaps. We must make sure these are zero.
		 */
		if (request.width < r->width ||
			request.height < r->height)
			vips_region_black(seq->composite_regions[j]);

		/* And render the right part of the input image to the
		 * composite region.
		 *
		 * If we are not in skippable mode, we can be completely
		 * outside the subimage area.
		 */
		if (!vips_rect_isempty(&request)) {
			VIPS_DEBUG_MSG("  fetching pixels for input %d\n", j);
			if (vips_region_prepare_to(seq->input_regions[j],
					seq->composite_regions[j], &request,
					hit.left, hit.top))
				return -1;
		}
	}

	VIPS_GATE_START("vips_composite_base_gen: work");

	for (int y = 0; y < r->height; y++) {
		VipsPel *q;

		for (int i = 0; i < seq->n; i++) {
			int j = seq->enabled[i];

			seq->p[i] = VIPS_REGION_ADDR(seq->composite_regions[j],
				r->left, r->top + y);
		}
		q = VIPS_REGION_ADDR(output_region, r->left, r->top + y);

		for (int x = 0; x < r->width; x++) {
			switch (seq->input_regions[0]->im->BandFmt) {
			case VIPS_FORMAT_UCHAR:
#ifdef HAVE_VECTOR_ARITH
				if (composite->bands == 3)
					vips_combine_pixels3<unsigned char,
						0, UCHAR_MAX>(seq, q);
				else
#endif
					vips_combine_pixels<unsigned char,
						0, UCHAR_MAX>(seq, q);
				break;

			case VIPS_FORMAT_CHAR:
				vips_combine_pixels<signed char,
					SCHAR_MIN, SCHAR_MAX>(seq, q);
				break;

			case VIPS_FORMAT_USHORT:
#ifdef HAVE_VECTOR_ARITH
				if (composite->bands == 3)
					vips_combine_pixels3<unsigned short,
						0, USHRT_MAX>(seq, q);
				else
#endif
					vips_combine_pixels<unsigned short,
						0, USHRT_MAX>(seq, q);
				break;

			case VIPS_FORMAT_SHORT:
				vips_combine_pixels<signed short,
					SHRT_MIN, SHRT_MAX>(seq, q);
				break;

			case VIPS_FORMAT_UINT:
				vips_combine_pixels<unsigned int,
					0, UINT_MAX>(seq, q);
				break;

			case VIPS_FORMAT_INT:
				vips_combine_pixels<signed int,
					INT_MIN, INT_MAX>(seq, q);
				break;

			case VIPS_FORMAT_FLOAT:
#ifdef HAVE_VECTOR_ARITH
				if (composite->bands == 3)
					vips_combine_pixels3<float,
						0, USHRT_MAX>(seq, q);
				else
#endif
					vips_combine_pixels<float,
						0, 0>(seq, q);
				break;

			case VIPS_FORMAT_DOUBLE:
				vips_combine_pixels<double,
					0, 0>(seq, q);
				break;

			default:
				g_assert_not_reached();
				return -1;
			}

			for (int i = 0; i < seq->n; i++)
				seq->p[i] += ps;
			q += ps;
		}
	}

	VIPS_GATE_STOP("vips_composite_base_gen: work");

	return 0;
}

/* Is a mode "skippable"?
 *
 * Skippable modes are ones where a black (0, 0, 0, 0) layer placed over the
 * base image and composited has no effect.
 *
 * If all the modes in our stack are skippable, we can avoid compositing the
 * whole stack for every request.
 */
static gboolean
vips_composite_mode_skippable(VipsBlendMode mode)
{
	switch (mode) {
	case VIPS_BLEND_MODE_CLEAR:
	case VIPS_BLEND_MODE_SOURCE:
	case VIPS_BLEND_MODE_IN:
	case VIPS_BLEND_MODE_OUT:
	case VIPS_BLEND_MODE_DEST_IN:
	case VIPS_BLEND_MODE_DEST_ATOP:
		return FALSE;

	default:
		return TRUE;
	}
}

static int
vips_composite_base_build(VipsObject *object)
{
	VipsObjectClass *klass = VIPS_OBJECT_GET_CLASS(object);
	VipsConversion *conversion = VIPS_CONVERSION(object);
	VipsCompositeBase *composite = (VipsCompositeBase *) object;

	int n;
	VipsBlendMode *mode;
	VipsImage **in;
	VipsImage **decode;
	VipsImage **compositing;
	VipsImage **format;

	if (VIPS_OBJECT_CLASS(vips_composite_base_parent_class)->build(object))
		return -1;

	n = composite->in->area.n;

	if (n <= 0) {
		vips_error(klass->nickname, "%s", _("no input images"));
		return -1;
	}
	if (composite->mode->area.n != n - 1 &&
		composite->mode->area.n != 1) {
		vips_error(klass->nickname, _("must be 1 or %d blend modes"),
			n - 1);
		return -1;
	}
	mode = (VipsBlendMode *) composite->mode->area.data;
	composite->skippable = TRUE;
	for (int i = 0; i < composite->mode->area.n; i++) {
		if (mode[i] < 0 ||
			mode[i] >= VIPS_BLEND_MODE_LAST) {
			vips_error(klass->nickname,
				_("blend mode index %d (%d) invalid"),
				i, mode[i]);
			return -1;
		}

		if (!vips_composite_mode_skippable(mode[i]))
			composite->skippable = FALSE;
	}

	in = (VipsImage **) composite->in->area.data;

	/* Make a set of rects for the positions of the input images. Image 0
	 * (the background) is always at (0, 0).
	 */
	if (!(composite->subimages =
				VIPS_ARRAY(NULL, n, VipsRect)))
		return -1;
	for (int i = 0; i < n; i++) {
		composite->subimages[i].left = 0;
		composite->subimages[i].top = 0;
		composite->subimages[i].width = in[i]->Xsize;
		composite->subimages[i].height = in[i]->Ysize;
	}

	/* Position all images, if x/y is set. Image 0
	 * (the background) is always at (0, 0).
	 */
	if (composite->x_offset &&
		composite->y_offset)
		for (int i = 1; i < n; i++) {
			composite->subimages[i].left =
				composite->x_offset[i - 1];
			composite->subimages[i].top =
				composite->y_offset[i - 1];
		}

	decode = (VipsImage **) vips_object_local_array(object, n);
	for (int i = 0; i < n; i++)
		if (vips_image_decode(in[i], &decode[i]))
			return -1;
	in = decode;

	/* Add a solid alpha to any images missing one.
	 */
	for (int i = n - 1; i >= 0; i--)
		if (!vips_image_hasalpha(in[i])) {
			VipsImage *x;

			if (vips_addalpha(in[i], &x, nullptr))
				return -1;
			g_object_unref(in[i]);
			in[i] = x;
		}

	/* Transform to compositing space. It defaults to sRGB or B_W, usually
	 * 8 bit, but 16 bit if any inputs are 16 bit.
	 */
	if (!vips_object_argument_isset(object, "compositing_space")) {
		gboolean all_grey;
		gboolean any_16;

		all_grey = TRUE;
		for (int i = 0; i < n; i++)
			if (in[i]->Bands > 2) {
				all_grey = FALSE;
				break;
			}

		any_16 = FALSE;
		for (int i = 0; i < n; i++)
			if (in[i]->Type == VIPS_INTERPRETATION_GREY16 ||
				in[i]->Type == VIPS_INTERPRETATION_RGB16) {
				any_16 = TRUE;
				break;
			}

		composite->compositing_space = any_16 // FIXME: Invalidates operation cache
			? (all_grey
					  ? VIPS_INTERPRETATION_GREY16
					  : VIPS_INTERPRETATION_RGB16)
			: (all_grey
					  ? VIPS_INTERPRETATION_B_W
					  : VIPS_INTERPRETATION_sRGB);
	}

	compositing = (VipsImage **) vips_object_local_array(object, n);
	for (int i = 0; i < n; i++)
		if (in[i]->Type == composite->compositing_space) {
			/* Already the right type ... just copy the image pointer
			 * and add a ref.
			 */
			compositing[i] = in[i];
			g_object_ref(in[i]);
		}
		else {
			if (vips_colourspace(in[i], &compositing[i],
				composite->compositing_space, nullptr))
			return -1;
		}
	in = compositing;

	/* Check that they all now match in bands. This can fail for some
	 * input combinations.
	 */
	for (int i = 1; i < n; i++)
		if (in[i]->Bands != in[0]->Bands) {
			vips_error(klass->nickname,
				"%s", _("images do not have same "
						"numbers of bands"));
			return -1;
		}

	if (in[0]->Bands > MAX_BANDS) {
		vips_error(klass->nickname,
			"%s", _("too many input bands"));
		return -1;
	}

	composite->bands = in[0]->Bands - 1;

	/* Set the max for each band now we know bands and compositing space.
	 */
	if (vips_composite_base_max_band(composite, composite->max_band)) {
		vips_error(klass->nickname,
			"%s", _("unsupported compositing space"));
		return -1;
	}

	/* Transform the input images to match in format. We may have
	 * mixed float and double, for example.
	 */
	format = (VipsImage **) vips_object_local_array(object, n);
	if (vips__formatalike_vec(in, format, n))
		return -1;
	in = format;

	/* We want locality, so that we only prepare a few subimages each
	 * time.
	 */
	if (vips_image_pipeline_array(conversion->out,
			VIPS_DEMAND_STYLE_SMALLTILE, in))
		return -1;

	/* The output image is always the size of the base image.
	 */
	conversion->out->Xsize = in[0]->Xsize;
	conversion->out->Ysize = in[0]->Ysize;

	if (vips_image_generate(conversion->out,
			vips_composite_start,
			vips_composite_base_gen,
			vips_composite_stop,
			in, composite))
		return -1;

	return 0;
}

static void
vips_composite_base_class_init(VipsCompositeBaseClass *klass)
{
	GObjectClass *gobject_class = G_OBJECT_CLASS(klass);
	VipsObjectClass *vobject_class = VIPS_OBJECT_CLASS(klass);
	VipsOperationClass *operation_class = VIPS_OPERATION_CLASS(klass);

	VIPS_DEBUG_MSG("vips_composite_base_class_init\n");

	gobject_class->dispose = vips_composite_base_dispose;
	gobject_class->set_property = vips_object_set_property;
	gobject_class->get_property = vips_object_get_property;

	vobject_class->nickname = "composite_base";
	vobject_class->description = _("blend images together");
	vobject_class->build = vips_composite_base_build;

	operation_class->flags = VIPS_OPERATION_SEQUENTIAL;

	VIPS_ARG_ENUM(klass, "compositing_space", 10,
		_("Compositing space"),
		_("Composite images in this colour space"),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET(VipsCompositeBase, compositing_space),
		VIPS_TYPE_INTERPRETATION, VIPS_INTERPRETATION_sRGB);

	VIPS_ARG_BOOL(klass, "premultiplied", 11,
		_("Premultiplied"),
		_("Images have premultiplied alpha"),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET(VipsCompositeBase, premultiplied),
		FALSE);
}

static void
vips_composite_base_init(VipsCompositeBase *composite)
{
	composite->compositing_space = VIPS_INTERPRETATION_sRGB;
}

typedef struct _VipsComposite {
	VipsCompositeBase parent_instance;

	/* For N input images, N - 1 x coordinates.
	 */
	VipsArrayInt *x;

	/* For N input images, N - 1 y coordinates.
	 */
	VipsArrayInt *y;

} VipsComposite;

typedef VipsCompositeBaseClass VipsCompositeClass;

/* We need C linkage for this.
 */
extern "C" {
G_DEFINE_TYPE(VipsComposite, vips_composite, vips_composite_base_get_type());
}

static int
vips_composite_build(VipsObject *object)
{
	VipsObjectClass *klass = VIPS_OBJECT_GET_CLASS(object);
	VipsCompositeBase *base = (VipsCompositeBase *) object;
	VipsComposite *composite = (VipsComposite *) object;

	int n;

	n = 0;
	if (vips_object_argument_isset(object, "in"))
		n = base->in->area.n;

	if (vips_object_argument_isset(object, "x")) {
		if (composite->x->area.n != n - 1) {
			vips_error(klass->nickname, _("must be %d x coordinates"), n - 1);
			return -1;
		}
		base->x_offset = (int *) composite->x->area.data;
	}

	if (vips_object_argument_isset(object, "y")) {
		if (composite->y->area.n != n - 1) {
			vips_error(klass->nickname, _("must be %d y coordinates"), n - 1);
			return -1;
		}
		base->y_offset = (int *) composite->y->area.data;
	}

	if (VIPS_OBJECT_CLASS(vips_composite_parent_class)->build(object))
		return -1;

	return 0;
}

static void
vips_composite_class_init(VipsCompositeClass *klass)
{
	GObjectClass *gobject_class = G_OBJECT_CLASS(klass);
	VipsObjectClass *vobject_class = VIPS_OBJECT_CLASS(klass);
	VipsOperationClass *operation_class = VIPS_OPERATION_CLASS(klass);

	VIPS_DEBUG_MSG("vips_composite_class_init\n");

	gobject_class->set_property = vips_object_set_property;
	gobject_class->get_property = vips_object_get_property;

	vobject_class->nickname = "composite";
	vobject_class->description =
		_("blend an array of images with an array of blend modes");
	vobject_class->build = vips_composite_build;

	operation_class->flags = VIPS_OPERATION_SEQUENTIAL;

	VIPS_ARG_BOXED(klass, "in", 0,
		_("Inputs"),
		_("Array of input images"),
		VIPS_ARGUMENT_REQUIRED_INPUT,
		G_STRUCT_OFFSET(VipsCompositeBase, in),
		VIPS_TYPE_ARRAY_IMAGE);

	VIPS_ARG_BOXED(klass, "mode", 3,
		_("Blend modes"),
		_("Array of VipsBlendMode to join with"),
		VIPS_ARGUMENT_REQUIRED_INPUT,
		G_STRUCT_OFFSET(VipsCompositeBase, mode),
		VIPS_TYPE_ARRAY_INT);

	VIPS_ARG_BOXED(klass, "x", 4,
		_("x coordinates"),
		_("Array of x coordinates to join at"),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET(VipsComposite, x),
		VIPS_TYPE_ARRAY_INT);

	VIPS_ARG_BOXED(klass, "y", 5,
		_("y coordinates"),
		_("Array of y coordinates to join at"),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET(VipsComposite, y),
		VIPS_TYPE_ARRAY_INT);
}

static void
vips_composite_init(VipsComposite *composite)
{
}

static int
vips_compositev(VipsImage **in, VipsImage **out, int n, int *mode, va_list ap)
{
	VipsArrayImage *image_array;
	VipsArrayInt *mode_array;
	int result;

	image_array = vips_array_image_new(in, n);
	mode_array = vips_array_int_new(mode, n - 1);
	result = vips_call_split("composite", ap,
		image_array, out, mode_array);
	vips_area_unref(VIPS_AREA(image_array));
	vips_area_unref(VIPS_AREA(mode_array));

	return result;
}

/* See conversion.c for the doc comment.
 */

int
vips_composite(VipsImage **in, VipsImage **out, int n, int *mode, ...)
{
	va_list ap;
	int result;

	va_start(ap, mode);
	result = vips_compositev(in, out, n, mode, ap);
	va_end(ap);

	return result;
}

typedef struct _VipsComposite2 {
	VipsCompositeBase parent_instance;

	VipsImage *base;
	VipsImage *overlay;
	VipsBlendMode mode;
	int x;
	int y;

} VipsComposite2;

typedef VipsCompositeBaseClass VipsComposite2Class;

/* We need C linkage for this.
 */
extern "C" {
G_DEFINE_TYPE(VipsComposite2, vips_composite2, vips_composite_base_get_type());
}

static int
vips_composite2_build(VipsObject *object)
{
	VipsCompositeBase *base = (VipsCompositeBase *) object;
	VipsComposite2 *composite2 = (VipsComposite2 *) object;

	if (composite2->overlay &&
		composite2->base) {
		VipsImage *in[3];
		int mode[1];

		in[0] = composite2->base;
		in[1] = composite2->overlay;
		in[2] = nullptr;
		base->in = vips_array_image_new(in, 2);

		mode[0] = (int) composite2->mode;
		base->mode = vips_array_int_new(mode, 1);
	}

	base->x_offset = &composite2->x;
	base->y_offset = &composite2->y;

	if (VIPS_OBJECT_CLASS(vips_composite2_parent_class)->build(object))
		return -1;

	return 0;
}

static void
vips_composite2_class_init(VipsCompositeClass *klass)
{
	GObjectClass *gobject_class = G_OBJECT_CLASS(klass);
	VipsObjectClass *vobject_class = VIPS_OBJECT_CLASS(klass);
	VipsOperationClass *operation_class = VIPS_OPERATION_CLASS(klass);

	VIPS_DEBUG_MSG("vips_composite_class_init\n");

	gobject_class->set_property = vips_object_set_property;
	gobject_class->get_property = vips_object_get_property;

	vobject_class->nickname = "composite2";
	vobject_class->description =
		_("blend a pair of images with a blend mode");
	vobject_class->build = vips_composite2_build;

	operation_class->flags = VIPS_OPERATION_SEQUENTIAL;

	VIPS_ARG_IMAGE(klass, "base", 0,
		_("Base"),
		_("Base image"),
		VIPS_ARGUMENT_REQUIRED_INPUT,
		G_STRUCT_OFFSET(VipsComposite2, base));

	VIPS_ARG_IMAGE(klass, "overlay", 1,
		_("Overlay"),
		_("Overlay image"),
		VIPS_ARGUMENT_REQUIRED_INPUT,
		G_STRUCT_OFFSET(VipsComposite2, overlay));

	VIPS_ARG_ENUM(klass, "mode", 3,
		_("Blend mode"),
		_("VipsBlendMode to join with"),
		VIPS_ARGUMENT_REQUIRED_INPUT,
		G_STRUCT_OFFSET(VipsComposite2, mode),
		VIPS_TYPE_BLEND_MODE, VIPS_BLEND_MODE_OVER);

	VIPS_ARG_INT(klass, "x", 4,
		_("x"),
		_("x position of overlay"),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET(VipsComposite2, x),
		-VIPS_MAX_COORD, VIPS_MAX_COORD, 0);

	VIPS_ARG_INT(klass, "y", 5,
		_("y"),
		_("y position of overlay"),
		VIPS_ARGUMENT_OPTIONAL_INPUT,
		G_STRUCT_OFFSET(VipsComposite2, y),
		-VIPS_MAX_COORD, VIPS_MAX_COORD, 0);
}

static void
vips_composite2_init(VipsComposite2 *composite2)
{
}

/* See conversion.c for the doc comment.
 */

int
vips_composite2(VipsImage *base, VipsImage *overlay, VipsImage **out,
	VipsBlendMode mode, ...)
{
	va_list ap;
	int result;

	/* Works for gcc and clang.
	 */
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wvarargs"

	/* Triggers a clang compiler warning because mode might not be an int.
	 * I think the warning is harmless for all platforms we care about.
	 */
	va_start(ap, mode);

	g_assert(sizeof(mode) == sizeof(int));

#pragma GCC diagnostic pop

	result = vips_call_split("composite2", ap, base, overlay, out, mode);
	va_end(ap);

	return result;
}
